A known display device can handle display modes, such as a normal mode, a newspaper mode, and a DICOM (Digital Imaging and Communication in Medicine) mode, to display various types of images. In the normal mode, a normal color image is displayed naturally. In the newspaper mode, characters in a newspaper are displayed in a manner similar to that of the newspaper. The DICOM mode has a gray scale so as to faithfully reproduce light and shadow of an X-ray image, as shown, for example, in Patent Document 1.